Over 10 million tons of biosolids from municipal sewage sludge are generated each year in the United States alone. The prevailing methods for the disposal of biosolids include the application of the biosolids to surface land application, such as to crop land, range land or forests, composting and landfill disposal. Each of these methods is associated with disadvantages.
For example, one disadvantage of the application of biosolids to surface lands is the resistance of persons living in the area of the application because of concerns about nuisances such as odor and wind-blown dust from the site of application. Biosolids application to surface land and landfills also creates risks for contamination of potable surface water and groundwater.
Further, disadvantageous weather conditions can delay the application of biosolids to surface land, and trucking biosolids to the application site creates pollution and nuisances. Additionally, the capacity for the disposal of biosolids by application to surface lands and landfills is limited and the associated costs are generally high. Also, greenhouse gasses, such as methane and carbon dioxide, are generated by the decomposition of the biosolids and these gases are released into the atmosphere at the sites of surface land application and most landfills.
Therefore, there is a need for an additional method for the disposal of biosolids that provides less risk for environmental contamination. Additionally, there is a need for an additional method for the disposal of biosolids that is less expensive. Further, there is a need for an additional method for the disposal of biosolids that does not permit the release of carbon dioxide and other green house gases into the atmosphere. Also, there is a need for an additional method for the disposal of biosolids that can produce usable byproducts from biosolids.